1. Field of the Invention
The present invention relates to a liquid seal structure for sealing oil and other liquid at a rotation shaft of an internal combustion engine, etc.
2. Description of Related Art
Conventionally, liquid seal structure has been used to with an internal combustion engine for preventing leaks of lubricant oil sealed inside a case at an output portion of a rotation shaft. Such liquid seal structure often also works for preventing invasion of dust from the outside.
U.S. Pat. No. 5,209,502 discloses a conventional liquid seal structure of rotation shaft.
As shown in FIG. 7 herein, the seal mechanism has a seal member 71 composed of a seal lip 71A made of Teflon (trademark of Dupont: polytetrafluoroethylene) or fluoropolymers in contact with an outer circumference of the rotation shaft 5 and dust seal lip 71B standing back to back with the seal lip 71A and in contact with the outer circumference of the rotation shaft 5, the seal member 71 sandwiched by an inner case 73 and an outer case 74 constituting a seal lip support member 72. The seal lip support member 72 is press-fitted to a housing 6 provided on a cylinder block of the engine.
The seal lip 71A is disposed toward the inside of the engine (liquid side) to seal the oil in the engine and the dust seal lip 71B is disposed toward the outside of the engine (gas side).
The seal lip 71A of the seal mechanism is a disc shape having inner diameter smaller than the diameter of the rotation shaft 5 and outer diameter larger than the diameter of the rotation shaft 5. The dust seal lip 71B has a disc shape having inner diameter smaller than the diameter of the rotation shaft 5 and larger than the inner diameter of the seal lip 71A and having the same outer diameter as the outer diameter of the seal lip 71A. When the rotation shaft 5 is pressed into the inner diameter of the seal lip 71A, the outer circumference of the rotation shaft 5 touches and slides on an end of the seal lip 71A, the contact surface being a seal surface 71C. At this time, inner end of the dust seal lip 71B also touches to the outer circumference of the rotation shaft 5. Further, a spiral groove 71D is formed on the seal surface 71C of the seal lip 71A against the rotation shaft 5, so that sealing can be made efficient using a pumping effect (an effect to push back oil etc.) of the groove 71D.
However, in the above-described seal mechanism, since the pumping effect is lost when the spiral groove 71D on the seal surface 71C of the rotation shaft 5 and the seal lip 71A is worn or when the groove 71D is packed by sludge, sealing effect can be lost to allow an oil leak.
Further, when the oil oozes out or leaks from the seal lip 71A, the oil can leak out to the outside through the dust seal lip 71B.
An object of the present invention is to provide a liquid seal structure capable of stably sealing for a long time.
A liquid seal structure according to the present invention is for preventing liquid on a liquid side from leaking toward a gas side, characterized in having: a tapered seal land provided on an outer circumference of a rotation shaft and having an outer circumference with a larger diameter on the liquid side than on the gas side; a tapered seal lip in contact with the outer circumference of the tapered seal land so that a contact surface forms a seal surface; and a seal lip support member for supporting the tapered seal lip.
According to the present invention, when the liquid, such as oil, invades into the seal surface between the tapered seal land and the tapered seal lip, since the seal surface is tapered, the liquid is returned to the side of the liquid to be sealed by moving elevationally, i.e. to the large diameter side of the tapered seal land on account of centrifugal force in accordance with the rotation of the rotation shaft. Accordingly, the liquid does not leak to the gas side, so that sealability can be secured for a long time to perform stable sealing. As a result, for instance, when the tapered seal lip has a groove. such as a helical groove, and sludge is packed in the groove or the groove is worn out, there is little influence on the sealing effect.
In the present invention, the tapered seal land is preferably independent from the rotation shaft and made of metal material, such as steel, sintered metal or metal sheets press-fitted to the rotation shaft. However, the rotation shaft itself may be carved to provide the tapered seal land. Plastic material may be used for the tapered seal land, however, since the tapered seal land can be heated during rotation, the aforesaid metal material is more preferable than the plastic material which is inferior in heat conduction.
The tapered angle of the tapered seal land is not specifically restricted but may be tapered in any manner from a gentle angle to a steep tapered angle, except for a right angle, as long as the liquid moves elevationally by the centrifugal force. Further, the width of the seal surface between the tapered seal land and the tapered seal lip is not specifically restricted but preferably as wide as possible. This is because the wider seal surface has a larger free-running effect (slinger effect) of the oil. Further, Teflon material is preferably used for the tapered seal lip, but other soft material having flexibility can also be used.
In the present invention, a groove may preferably be formed on at least one of the contact surfaces of the tapered seal land and the tapered seal lip.
According to the above arrangement, the leaked liquid goes into the groove and is unlikely to advance further outside in addition to the elevational movement of the liquid, such as oil, by the centrifugal force in accordance with rotation of the rotation shaft, thus obtaining further sealability. Further, when the groove is a helical groove, further improved sealability can be secured by the pumping effect of the groove
In the above, the groove includes helical grooves and multiple grooves. The depth of the groove is preferably approximately half (40 to 50%) of lip thickness. When the groove is a helical groove, the helix direction of the helical groove is the direction for pushing back the liquid, such as oil, though different in accordance with the rotation of the rotation shaft.
In the above, a dust seal lip for preventing invasion of dust from the gas side may preferably be provided on the outer circumference of the rotation shaft.
According to the above arrangement, since invasion of the dust or the like from the outside to the side of the liquid to be sealed can be prevented, damage on the seal surface between the tapered seal land and the tapered seal lip can be prevented, thus improving durability of the liquid seal structure.
In the above arrangement, the dust seal lip may be integrated with the tapered seal lip or may be provided as an independent body.
In the above liquid seal structure, the tapered seal lip and the dust seal lip may be integrated.
Accordingly, since the tapered seal lip and the dust seal lip are not necessary to be manufactured separately, production labor can be reduced.
Alternatively, the tapered seal lip and the dust seal lip may be independently formed.
Accordingly, since the tapered seal lip and the dust seal lip are separate bodies, the tapered seal lip and the dust seal lip can be manufactured easily. Further, since the dust seal lip can be formed in an appropriate form, the dust sealing property can be improved.
The liquid seal structure of the present invention may preferably have a liquid pool provided on the outer circumference of the tapered seal land for collecting the liquid.
Accordingly, even when the liquid leaks out from the seal surface between the tapered seal land and the tapered seal lip, the liquid is collected in the liquid pool, so that liquid leakage to the outside can be prevented by a self-collection function where the liquid moves to a lower part of the shaft through the groove and is collected again to the inside of the engine. Therefore, sealability can be secured for a long time to perform stable sealing.
In the above, the liquid seal structure may further include: a seal member opposite to the liquid pool; and a cylindrical liquid block on a surface of the seal member opposite to the liquid pool.
Accordingly, the liquid, such as oils leaked through the seal member is blocked by the liquid block to be dropped into the liquid pool. The liquid in the liquid pool moves to the lower part of the shaft and is re-collected to the inside of the engine by the self-collection function, so that the leakage of the liquid to the outside can be prevented, thus securing sealability for a long time.
The configuration of the liquid block is not restricted as long as the liquid transmitted through the seal member can be blocked. For instance, the liquid block may be a projecting portion formed by cutting into the inner circumference of the seal member, or a molding having square or triangle cross section attached to the inner circumference of the seal member.
In the liquid seal structure according to the present invention, a liquid pool for collecting the liquid may alternatively be provided on an inner circumference of the tapered seal lip.
Accordingly, even when the liquid leaks out from the seal surface between the tapered seal land and the tapered seal lip, the liquid is collected in the liquid pool, so that liquid leakage to the outside can be prevented by the self-collection function where the liquid moves to a lower part of the shaft through the groove and is collected again to the inside of the engine. Therefore, sealability can be secured for a long time to perform stable sealing. Since both of the components are not manufactured separately, production labor can be reduced.
In the above arrangement, a seal land may preferably be provided opposite to the liquid pool and a cylindrical liquid block may preferably be provided on a surface of the seal land opposite to the liquid pool.
According to the present invention, the liquid leaked out from the seal surface between the tapered seal land and the tapered seal lip is blocked by the liquid block and drops to the liquid pool. The liquid in the liquid pool moves to the lower part of the shaft and is re-collected to the inside of the engine by the self-collection function, so that the leakage of the liquid to the outside can be prevented, thus securing sealability for a long time.
In the above, a diameter at which the seal land and the seal lip touches on both ends of the liquid pool in an axial direction of the rotation shaft may preferably be larger on the liquid side than on the gas side.
According to the above arrangement, since the liquid collected in the liquid pool moves in a direction elevating by the centrifugal force, i.e. larger diameter side, the leakage of the liquid to the outside can be prevented, so that sealability can be secured for a long time.
In the above, the seal member may preferably be integrated with at least one of the tapered seal lip and the dust seal lip.
Accordingly, since both components are not necessary to be made separately, production labor can be reduced.
In the above, the tapered seal land may preferably be independent from the rotation shaft.
Accordingly, since the tapered seal land can be easily manufactured by changing the tapered angle as desired and complicated processing on the rotation shaft is not necessary, production labor for the process can be omitted.